1

Air Force Satellite Control Network Interoperability

Space Internet Workshop #4June 2004

John PietrasGlobal Science and Technology, Inc

2

Contents

• Background of the AFSCN Interoperability Project• CCSDS Space Link Extension – candidate for AFSCN

interoperability• Summary of Interoperability Project Phase 3

– Completed in Summer 2003

• Transition from legacy- to standards-based infrastructure• Overview of Phase 4 activities

– Spring-Summer 2004

• Interoperability with other US space organizations

3

AFSCN Interoperability Project Background

• Project is managed by AF Space and Missile Systems Command Satellite and Launch Control SPO as part of AF Satellite Control Network (AFSCN) modernization program

• Space vehicles to be supported will use legacy AFSCN radio frequency (RF) and modulation standards for another decade

• Goals– Adopt/define services that will facilitate interoperation among US government

satellite ground control networks– Base services on packet-switched network technology to continue the AFSCN’s

migration from circuit-switched technology

• Approach– Adopt existing space data standards where available and appropriate– Adapt standards where necessary– Feed enhancements back to standards community for broader acceptance– Feed results into Satellite Control Network Contract (SCNC) Architecture

development

• Multi-phase study and demo project started in 2001– Phase 1: Standards assessments and lab tests– Phase 2: Field tests with AF R&D assets– Phase 3: Field tests with commercial and civil agency ground stations– Phase 4: Develop standards profile for national infrastructure, field test vendor

implementations

4

CCSDS Space Link Extension – Candidate for AFSCN Interoperability

• Consultative Committee for Space Data Systems (CCSDS) has developed standards for the exchange of space vehicle (SV) command and telemetry data between mission ground facilities (e.g., satellite operations centers) and TT&C ground stations– Dubbed Space Link Extension (SLE) because they extend the space

link protocols across the terrestrial WAN

– Originally developed to transport CCSDS-defined space link data units

• Adoption of SLE by the international civil space community makes SLE attractive as interoperability standard for AFSCN

• Adaptations to CCSDS SLE services were prototyped and demonstrated in Interoperability Phases 1 & 2– SLE Return All Frames (RAF) service adapted to support AFSCN’s

time-correlated streaming telemetry (in contrast to discrete CCSDS space link data units)

– SLE Forward Communication Link Transmission Unit (FCLTU) service adapted to support time-critical streaming command data

5

CCSDS Space Link Extension Services

Domain of

Space LinkExtension

• Standard services for exchanging space link data between ground termination of the space link and remote users

– Evolution of mission-unique/provider-unique services– Formally assumes that CCSDS link protocols are used on the space-ground link

• AFSCN project has loosened even this assumption– Appropriate for missions that do not use Internet-interoperable protocols

Control Center

Return Link DataProcessing Facility

CCSDS (or legacy) space link interface

CCSDS (or legacy) space link data

structures tunneled thru IP WAN

6

VPNVPN

Phase 3 Service Architecture

RF & Mod

FCLTU (cmd)

ioNET cmd)

RAF (echo)

Johns Hopkins UniversityApplied Physics Lab

(JHU APL) Laurel, MD

ioNET (echo)

ioNET (tlm)

RF &Mod

FCLTU (cmd)

RAF (echo)

NOAA Command and Data Acquisition (CDA) Wallops Flight Facility, VA

RAF (tlm)

RF &Mod

NASA Experimental 5.4 m,Wallops Flight Facility, VA

RAF (tlm)

COBRASV C2 system

FCLTU (cmd)

ioNET cmd)

RAF (echo)

CERES SOC

ioNET (echo)

ioNET (tlm)

RAF (tlm)

COBRA COTS-based Research ArchitectureFCLTU Forward Communication Link Transmission Unit (CCSDS SLE)ioNET Avtec multiplexer/demultiplexer system RAF Return All Frames (CCSDS SLE)TACO Test And CheckOut SV Dual connectivity: Internet and dedicated T1 Internet connectivity only

RAF (trk)

RAF (trk)Az/El

GST implementation

Avtec implementation

TACO 1

TACO 2

TACO 3

7

•SLE-SM SOC application

•Service status display

Email client

CERES SOC

NASA WFF

Internet Service Request and Response

XML files

WFF Sched/Mgmt system(s)

Email client & SLE-SM provider application

DataLynx Ops CenterColumbia, MD

JHU APLDataLynx Sched/Mgmt system

Service Request and Response XML file email attachments

Phase 3 Service Management Interfaces

Email client & SLE-SM provider application

1/sec service status messages

8

Summary of Phase 3 Results*

• Telemetry– Use of TCP and data buffering (~2-4 seconds additional delay) provided

reliable delivery of the serial telemetry stream– Telemetry TDC of SLE RAF implementation was accurate to within

several tens of milliseconds, but not required 1 msec– ioNET TDC was accurate to within 1 msec, but 170kbps digitized IRIG-

B signal deemed overly consumptive of bandwidth• Command

– Time-critical commanding was successful using both the FCLTU and ioNET based implementations

• Command echo– Command echo was successful using both the RAF and ioNET based

implementations• Service Management

– Contacts scheduled using SLE standard format schedule requests/responses

– Ad hoc methods needed for tracking data and ground station status

* Full results are documented in the SCNC Interoperability Phase 3 Project Report, Honeywell Technology Solutions, Inc. 28 October 2003, prepared by Lance Williams

9

Transition from Legacy to Standards - Based Infrastructure (1 of 3)

• 3 reference points for a transition architecture – RF & modulation interface with the SV

• Currently SIS-502D– New standards-based interoperable interface between ground station

and SOC– Telemetry, command, and command echo interface as seen by the user

C2 system• Currently SIS-508E

Ground Station SOC

CommunicationSegment

RangeSegment

Current AFSCN

C2 System

SIS-502 interoperable SIS-508 I/F

Remains in place as long as compliant

SVs are flying

Put in place ASAP Can be replaced or eliminated as SOC technology and

designs evolve

10

Transition from Legacy to Standards - Based Infrastructure (2 of 3)

• 3 sets of “standards” to enable interoperability for AFSCN-client SVs using SLE transfer services – SLE service production specifications that define the processing required to

transform the data transferred by the SLE transfer service to/from RF• Currently SIS-502D

– SLE transfer service specifications provide the interoperable interface– SLE service adaptation specifications that define the required transformations

between SLE and legacy user interfaces• Currently SIS-508E

Ground Station SOC

SLE TSentity

SGLS/SLE service production

Current AFSCN

C2 System

SIS-502 SLE Transfer SIS-508 Service

SLE TSentity

SIS-508/ SLE

adaptation

11

Packet mode C2 system eliminates

Adaptation

USB augmentsSGLS

Transition from Legacy to Standards - Based Infrastructure (3 of 3)

• Adaptations eventually disappear as SOC designs natively incorporate SLE transfer services

• SLE service productions evolve with SV evolution

Ground Station

SLE TSentity

SGLS/SLE service production

SLE TransferSIS-502 Service

Ground Station

SLE TSentity

SGLS & USB/SLE service production

Updated SIS-502

SOC

SLE TSentity

SOC

AFSCN packet modeC2 System

SLE TSentity

AFSCN packet modeC2 System

12

Phase 4 Implementation of SLE Services• Telemetry

– Vendor-supported implementation of prototype modifications of RAF SLE service to transfer and time-correlate serial stream of telemetry data

• Command– Vendor-supported implementation of prototype modifications of

FCLTU SLE service to transfer AFSCN SGLS-formatted command data

– SGLS command FCLTU service supports two modes:• Discrete commands (inter-command idle added at ground station)• Streaming commands (all symbols, including inter-command idle)

used to transfer discrete commands

• Command Echo– Vendor-supported implementation of prototype modifications of

RAF SLE service to transfer serial stream of command echo symbols

• Service Management– Continue exploring use of SLE scheduling and configuration

standards

13

Establishing Interoperability With Other US Space Organizations

• Telemetry– Develop new CCSDS Return Telemetry (RT) SLE service

• Supports AFSCN serial telemetry• Supports civil space needs not met by current RAF SLE service • CCSDS Birds of a Feather (BOF) group formed

– Adopt time-correlated telemetry adaptation in 508-legacy AFSCN SOCs

• Command– Adopt SGLS command production for FCLTU as US national

interoperability capability• USTAG13 BOF group formed

– Adopt SGLS command adaptation in 508-legacy AFSCN SOCs• Command echo

– Adopt SGLS command echo production for RT service as US interoperability capability

– Adopt SGLS command echo adaptation in 508-legacy AFSCN SOCs

14

Acknowledgements

• U.S. Air Force Space and Missile Systems Center Satellite and Launch Control SPO (SMC/RN)– AJ Ashby, 1Lt, USAF, project officer– Carl Sunshine, The Aerospace Corporation, technical lead

• Satellite Control Network Contract – Lance Williams, Interoperability project lead– JHU APL ground station

• AF Center for Research Support (CERES)• NASA WFF and NOAA Wallops CDA ground stations• Avtec Systems• General Dynamics Advanced Information Systems

15

Phase 4 Participants

• U.S. Air Force Space and Missile Systems Center Satellite and Launch Control SPO (SMC/RN)

• Satellite Control Network Contract • The Aerospace Corporation• GST, Inc.• AF Center for Research Support (CERES)• Avtec Systems • NOAA WFF• GD-AIS• L3Com• RTLogic • JPL, NASA